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Old 03-13-2011, 05:24 PM   #122 (permalink)
gone-ot
...beats walking...
 
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Quote:
Originally Posted by euromodder View Post
The diameter does change - when measured from the contact point through the hub to the top) .
That's what lifts the vehicle when the tyres are pumped up.

What doesn't really change due to inflation pressure is the tyre's circumference.
...true for the "unloaded" circumference, but NOT true for the "loaded" circumference.

...simple test: (1) measure the circumference of a tire; (2) paint a white spot on that tire; (3) drive exactly 5,280 ft measured mile at a slow speed and video record the whole distance; (4) review the video, counting exactly how many "tire revolutions" occur. I'll guarantee the number is greater than the mathematical number derived from dividing the tires' circumference-in-feet into 5,280...the video "count" will be close to 3-4% higher than the mathematical number...and that difference is because the "loaded" circumference is SMALLER than the "unloaded" circumference.

...unless you're driving on fuelly-slicks, circumference won't "grow" too much during normal driving...but it actually does at high speeds with high profile sidewall tires.
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